The conclusions of this publication are that a qualified electrician should make the change and that you should search for pleasing lighting TLED systems before you buy any. TLEDs are promoted as common replacements for fluorescent lamps. Most vendors and utilities simply replace lamps one for one, which is often the cheapest and most expedient solution, but not always the best. Here are some sample questions:
- Has the use and occupancy of all the spaces served changed at all since the original lighting was installed?
- Will the amount and distribution of light with new LEDs be suitable or correct?
- Should more or less lighting be provided?
- Should some light fixtures be added or removed?
- Should new LED fixtures be installed instead of using old existing fixtures?
- If using third party electric generation suppliers, will reductions in consumption result in supplier contract charges?
- Are there rebates available and who gets them?
- Are local government or electrical permits needed?
- Do your insurance carriers have any concerns?
An LED is a chip with two wires attached. The chip is a diode that allows power to travel in only one direction. It’s like an electronic check valve. With just the right amount of power through the wires, the chip lights up. The power is a direct current (DC), rather than alternating current (AC) because DC moves only in one direction while AC changes direction continuously. Most LED bulbs and tubes are supplied with AC power, so a device has to convert AC to DC in order for an LED to light. That device is called a driver.
The emitted LED light shines only in one direction. To make an LED bulb, many LED chips are pointed in various directions, usually filtered through a translucent enclosure. The same is true for an LED tube. The LEDs are usually installed in a straight line inside, shining through a translucent tube wall to imitate the appearance of a fluorescent tube.
AC powers fluorescent light fixtures. Electricity lighting the gases inside fluorescent tubes is usually controlled by a transformer, called a ballast. The older ballasts were electromagnetic, and the newer ones are electronic. Some TLED tubes are compatible with existing fluorescent ballasts. There are three types of TLED tubes:
- T8 Electronic Ballast powering compatible TLED tubes
- Direct Wired or Ballast Bypass TLED tubes with built-in integral driver
- TLED tubes powered by either an integral driver or a T8 electronic ballast (combo tube)
The important concept here is that electricians who replace fluorescent tubes with LED tubes and their drivers have to know what they are doing. For example, if the change violates a safety rating, such as approval by Underwriters Labs (UL) or the National Electric Code (NEC) and causes a fire, most insurance may not cover the resulting damage. This can be significant.
The quality of light from a tubular LED fixture is determined by three factors. One is the color temperature of the light, described in Kelvin (K) degrees. If you want a room to look depressingly and starkly blue, choose a color temperature of about 5,000oK or higher. If you want a room to look pleasantly warm, choose a color temperature of perhaps 3,500oK or lower.
A second factor in the quality of light is its color rendering index, CRI. Sunlight has a CRI of 100. All artificial light has a lower rating, which makes light reflected off colored surfaces of less quality than sunlight. A CRI of 80 or higher is usually adequate.
The third quality factor is glare. An electric plasma arc flowing through a fluorescent tube produces ultraviolet light. Phosphors on the inside surface of the tubes change the ultraviolet light into more even and pleasant colors of visible light. The newer fluorescent tubes that are one inch in diameter (T8) have a combination of three phosphors to improve the quality of the light. Yet, glaring light from bare fluorescent tubes of any type can be diffused by prismatic, egg-crate, shell or parabolic lenses or diffusers, or even light from the interior surfaces of a fixture, reflected by an opaque cover that hides the direct glare of fluorescent tubes completely. Since TLED tubes have one-directional light, glare has to be even more carefully controlled. Phosphors inside fluorescent replacement tubes are replaced with translucent plastic tubes enclosing the strips of LEDs. Some LEDs are installed within thin, uniformly lit panels.
Like the choice of TLED tube types, the choice of the fixtures that enclose them is equally important. Try one or two before you buy dozens.
The choice of TLED tubes and their drivers is made much more complicated if those tubes need to be dimmed. The type of dimming system must be compatible with the TLED drivers. Several manufacturers produce dimming systems that are compatible only with certain drivers, limiting the choice of system to proprietary combinations. Again, the electricians that install the TLED tubes, drivers and dimming systems must thoroughly understand which combinations will produce functional and attractive lighting projects.
TLED tubes last longer than fluorescent tubes, and they use less electricity. But, you must pay attention to the many details involved with their installation. For example, if you install a TLED tube powered by 120 volts, without labeling the fixture, someone might later replace it with a low voltage TLED tube that is intended for use with an LED driver, which may cause problems.
If electric heat is used, you will not see any reduction in electric use in winter. This is because the more efficient LEDs generate less heat, which is made up by the electric heating system. With any other type of heat, there will be an increase in fuel consumption in winter for the same reason. In summer there should be reductions in both lighting electricity and in cooling electricity.
Our thanks to Neil Sobel of ALI Lighting and Carl Watson P.E., L.C. for help with this article.